FLIGHT OF FLYING- FISHES. 



471 



from the Agra Aerological Laboratory. The balloons were sent 

 up at the time I w^as making my measurements. On one day 

 seven balloons were let oft' while I was observing. From data 

 thus obtained, it was possible to deduce the speed of the vultures 

 through the air. 



Another set of measurements were made by me during the 

 hrst eiglit months of the year 1915. In these cases, however, 

 the balloons had been liberated four or five hours before my ob- 

 servations were made. An error is thus introduced into the 

 calculations which, it may be noted, is likely to l)e less on days 

 of light wind than in stronger winds. 



The results of these two sets of observations agree in indicating 

 that vultures soar at higher speeds in stronger winds. The mean 

 speeils calculated from my data are as follows : — 





Observations made in 

 April January to 

 1920. August 1915. 



Vel(jcities of wind, in which 



Mean speed of vultures, in 



the vultures were flying", 



metres per second. 



in metres per second. 





0-3 



11-G 11-7 



4-6 



11-8 14-1 



7-9 



15-0 17-2 



10-20 



20-0 17-7 



The above figures are based on 122 observ^ations made in 

 April 1920 and (5915 observations made in 1915. 



Reasons have been adduced by me for believing that the 

 vultures on which the above measurements were made, were, as 

 they appeared to be, actually in horizontal flight and that their 

 speed, which they can maintain indefinitely, cannot be explained 

 by loss of height. An additional reason may here be mentioned 

 for this belief. It is that if a vulture glides, in soarable air, with 

 even a small loss of height, its speed will very greatly inci-ease 

 beyond the above figures. For instance, in April last a measure- 

 ment was made of a speed of 42 metres per second in a vulture 

 flying nearly with the wind. The wind had a velocity of only 

 2^ metres per second at the height at which the vulture was 

 flying. Hence the speed of the bird through the air must have 

 been abont 40|J metres per second. As this speed was exceptional 

 and as the l)ird was travelling in the direction of a place where 

 vultures frequently settle, it was assumed that it ^\ as gliding with 

 loss of height, though no loss of height was seen, and it was not 

 included in the calculation of the mean speeds above given. 



If vultures in soaring flight attain velocities of ten to twenty 



